1. Answers
Remember the change in absorbance takes place because the enzyme is digesting the protein in the milk powder solution. What is happening in the cuvette at pH7? Use the words protein, amino acids, soluble, insoluble, hydrolysis, enzyme =protease (neutrase) in your answer. (3 marks)
Which is the optimum pH for neutrase? (1 mark) What is the evidence from the data for this?(1 mark)
The textbook value for optimum pH for neutrase is Do your results agree with this? (1 mark)
Why is using the colorimeter better than just taking the time the milk takes to clear by eye for each pH?(1 mark)
Can you criticise any of the plot lines (e.g. are they all smooth)? (1 mark)
Why may these anomalies have occurred? (2 marks)
How could you make the experiment more reliable? (3 marks)
Why did we use buffer solutions?
The insoluble protein was hydrolysed to soluble amino acids by protease
7, solution went clear the fastest
Yes, these worked in the experiment
The end point was measured, not guessed
pH8 not clear fast enough, some lines e.g. pH4 wonky maybe due to light getting in or milk powder floating about
See last ans
Repeat each dilution 3 times, ignore anomalies, average other results.
To maintain pH within a narrow range

2. 3.1.2 factors affecting enzyme action
p.33
Description and explanation of the effect of temperature, pH, substrate concentration, enzyme concentration on the rate of reaction

3. Collection of a gas the displacement method
Draw a scientific diagram of collection of a gas used in the experiment

4. Group content The effect of temperature on enzymes
The effect of pH on enzymes
The effect of substrate concentration on enzymes
The effect of enzyme concentration on enzymes (practical demo)

5. Group work In your group split up the work into
Description of the effect of your factor
Graph to support this
Use the induced fit model of enzyme action to explain the effect of your factor on the enzymes action
You will have to prepare (15mins) and present your information to the rest of the group
Resources text p.33-5, old as text p. 62-5
You may use OHT/whiteboard and pens to present

6. What factors affect enzymes?
The rate of an enzyme-controlled reaction is affected by several factors:
temperature pH
enzyme concentration
substrate concentration.
Each enzyme works best within a range of conditions, and this range is different for each enzyme.
Photo credit: New Brunswick Scientific
A BioFlo™ Pro fermentor from New Brunswick Scientific, Edison NJ, USA.
Teacher notes
A fermentor, such as the one in the image, is a vital piece of equipment in the industrial use of enzymes as it makes it relatively easy to monitor and maintain optimum conditions.
Enzymes are also affected by the presence of inhibitors.

7. Measuring the initial rate of reaction

8. Effect of temperature on enzymes
Teacher notes
Students could be asked if they can deduce the equation for calculating the Q10 of this reaction based on the data from this graph.
Q10 = rate of reaction at x + 10 °C / rate of reaction at x °C

9. Effect of pH on enzymes

10. Effect of substrate concentration on rate

11. Effect of enzyme concentration on rate

12. Factors affecting rate of reaction

13. Rate of reaction experiment

14. Answer to table temp Time (s) Rate (1/sec) 5 No change 10 15 20 47610 15 20
476
0.0021 25
333
0.0030 30
242
0.0041 35 82
0.0122 40 63
0.0159 45
137
0.0073 50
244 55 60

15. 1 mark
4 marks
So they were at the right temp. before they react together
37-39 from graph
5,10,15 enzyme/substrates have little kinetic energy, few successful collisions forming enzyme substrate complexes. 55,60 bonds holding tertiary structure broken, active site wrong shape to fit substrate
5cm3 milk, 5cm3 water/boiled enzyme

16. Enzymes and structure worksheet

17. 4 marks
Did not predict effect of denaturing
6cm3min-1
cm3min-1
0-45C as temp rises oxygen production increases, more KE, more successful collisions so more ESC formed as temp increases rate of oxygen production decreases, too much KE so bonds holding tertiary structure broken, active site wrong shape to fit substrate
pH, enzyme concentration, substrate concentration

18. Enzymes and temperature worksheet

19. 4 marks
pH7
pH4-7 as increase in pH the rate of reaction increased, pH 7-9 as increase in pH rate of reaction decreased, in acid or alkaline the H+ or OH- interact with the bonds in the enzyme causing bonds holding the tertiary structure to be broken so the active site is no longer the right shape to fit the substrate (can’t form ESC)
Placing in a buffer solution, keeps the pH within a narrow range
Temp, enzyme concentration, substrate concentration

20. Enzymes and pH worksheet

21. 1 a add iodine solution, brown to blue black
1b add Benedicts and heat, goes from blue to brick red ppt
1 c add Biuret solution, goes from blue to purple
A only one + for all
C only one + for starch and protein but – for reducing sugar
E only one – for starch

22. Substrate concentration
Flat - enzyme working at its maximum rate, all active sites are full, substrates are queuing up to get into the active site
Temperature – too low not enough KE/too high dentaured, pH too high/low = denatured, enzyme concentration – increase will increase rate teaction
Time substrate is used up, time takes for product to form, rate = 1/time
At ow substrate concentration inhibitor combines with active site, as it is a similar shape to the substrate, at high substrate concentrations inhibitor is out competed by the substrate
Non competitive inhibitor binds at a different place than the active site, causes the shape of the active site to change, prevents formation of enzyme substrate complexes

23. Mark/14 Biological Catalysts Activation Proteins Shape Active site
Enzyme-substrate complex
Optimum
Denatured
Competitive
Non-competitive
Increases
Mark/14

24. Totals
Total/83
Grade
(%) 66 A 80 58 B 70 50 C 60 42 D 33 E 40